chesstutorapp app for iPhone and iPad
Learn to play better chess. Playing through real examples of Grandmaster games you are challenged to find the move made by the masters. For any move that you make you will receive a score (where 100% is where you found the right move (or one just as good) and 0% is where you make a move that would have led to certain defeat (such as throwing your queen away). You also receive advice in natural English language about why the move you played was not optimal. Monitor your average score in each game. At the end of each game you even get an estimate of your Elo rating (just for fun).